Engineering Mechanics Commons^™

Me-Em Enewsbrief, March 2011, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Me-Em 2011 Annual Report, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering Annual Reports

Table of Contents

• ME-EM: 85 Years of Excellence
• Faculty & Staff
• Enrollment & Degrees
• Alumni
• Resources
• Graduates

Anomalous Loss Of Toughness Of Work Toughened Polycarbonate, Shawn E. Meagher

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Glassy polymers such as polycarbonate (PC) can be toughened through compressive plastic deformation. The increase in toughness is substantial, showing as much as a fifteen fold increase in the amount of dissipated energy during failure for samples compressed to 50% plastic strain. This toughness increase can be reversed through thermal aging at temperatures below the glass transition temperature (T_g = 147°C).

The combined effect of plastic compression and thermal aging has been studied using Charpy, Single Edge Notch Bending (SENB), and Compact Tension (CT) tests. The tests mapped the response of samples cut along different orientations relative to the …

Hybrid Nanomanufacturing Process For High-Rate Polymer Nanofiber Production, Chad T. Peterson

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Nanotechnology and nanomaterials have the potential to revolutionize existing and create entirely new industries. Unique physical, mechanical, chemical, and biological properties of nanomaterials have been extensively documented in the last two decades. However, most nanomaterials are discontinuous in nature, creating problems with their processing and manipulation into devices and raising health concerns. Continuous nanofibers represent an emerging class of nanomaterials with critical advantages to applications. Continuous nanofibers are readily produced by electrospinning process comprising spinning polymer solutions in high electric fields. Electrospinning is a very economic top-down nanomanufacturing process that has been used to produce ultrafine continuous nanofibers from several …

Me-Em Enewsbrief, December 2010, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Nanomanufacturing And Analysis Of Novel Integrated Continuous Nanofibers, John E. Hannappel

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Complex nanostructured materials have great potential for applications in many areas of nanotechnology. This potential is being unlocked by precise control of their nanoscale architecture and properties. Most current methods of creating these nanostructures are expensive and difficult to control, with the majority of techniques resulting in non-continuous nanostructures and nanoparticles. Electrospinning is an economic nanomanufacturing method resulting in continuous nanofibers. The method consists of spinning fiber-forming liquids in high electric fields. In this work, a modified electrospinning process was analyzed. The process utilized two concentric liquids that resulted in integrated continuous hollow or composite nanofibers. A new adjustable co-axial …

Me-Em Enewsbrief, September 2010, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Diffuse Ultrasonic Scattering In Advanced Composites, Christer Stenström

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Non destructive testing (NDT) is a noninvasive technique used for characterization and inspection of the integrity of objects. NDT is an important tool for research, manufacturing monitoring and in-service inspections. Ultrasonic testing is the most used NDT technique, which for advanced composites can identify several types of defects, like delamination and interlaminar cracks. Diffuse ultrasonics has shown to be able to extract information at the microscale of metals and therefore it is believed it can be used for advanced composites to extract microstructural information, i.e. at the level of fibers.

In this thesis, diffuse ultrasonic methods, together with spatial variance …

Me-Em Enewsbrief, June 2010, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Mechanical Milling Of Co-Rich Melt-Spun Sm-Co Alloys, Farhad Reza Golkar-Fard

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Rare-earth, high-energy permanent magnets are currently the best performing permanent magnets used today. The discovery of single domain magnetism in 1950’s ultimately led to the development of nanocomposite magnets which had superior magnetic properties. Previous work has shown that mechanical milling (MM) effectively generates nanoscale structures in Sm-Co-based alloys. MM of more Co-rich, melt-spun Sm-Co alloys (up to the eutectic composition) and the role of initial structure on the milling behavior were investigated.

Sm-Co alloys with compositions of Sm_10.5Co_89.5 and Sm₈Co₉₂ were produced by arc melting, melt-spinning and mechanical milling. X-ray diffraction results showed …

Coupled Dem-Fem For Dynamic Analysis Of Granular Systems In Bending, Kitti Rattanadit

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Characterizing the dynamic behavior of granular materials is one of the great challenges in the mechanics of granular matter. Methods for evaluating the mechanical properties of granular matter have applications in a variety of industries, mining and geotechnical activities, defense and military operations. A coupled 2D Discrete Element Method-Finite Element Method (DEM-FEM) code, called "BobKit", is developed and implemented for analyzing the behavior of a 2D granular layer on top of an elastic beam under deforming (quasi-static) or vibrating (dynamic) of the beam. The explicit time-integration dynamic code is used to simulate quasi-static and dynamic bending of the granular layer …

Me-Em Enewsbrief, March 2010, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Me-Em 2010 Annual Report, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering Annual Reports

Table of Contents

• First Year to First Career
• Faculty & Staff
• Alumni
• Resources
• Graduates
• Publications

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha, Florin Bobaru

Department of Engineering Mechanics: Faculty Publications

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …

Design, Reconstruction And Evaluation Of A Dynamometer For Quarter Scale, Samuel Sanchez

BioResource and Agricultural Engineering

This project discusses the design, reconstruction, and evaluation of a dynamometer. A new test stand for the Quarter Scale team would improve the testing of the engines and the Continuously Variable Transmission (CVT). All the readings will be done electronically in order to provide the most accurate data collection. The dynamometer will be a closed hydraulic system for ease of use. This system will be able to test all of Quarter Scale engines. The data collected will be used to determine which engines are in the best condition, and which may need to be fixed. With the new design, the …

Me-Em Enewsbrief, December 2009, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Indentation Creep Analysis For Self Similar Indenters, Sandeep V. Thube

Mechanical & Aerospace Engineering Theses & Dissertations

In indentation creep experiments, it is difficult to characterize the mechanical properties of small size specimens using conventional methods. This study uses finite element modeling to investigate rate-sensitive deformation of materials with different hardness and strain rate sensitivities for self similar indenter tip geometries. The simulation model is developed using commercially available finite element software Abaqus/Standard. Our study investigates the difference between strain rate sensitivity of hardness (vH) and of flow stress (vu) and their relation to the hardness/modulus ratio. It reveals that the commonly held assumption that vH = vu is violated except for materials with low hardness/modulus …

Me-Em Enewsbrief, September 2009, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

The Effects Of Combined Compression And Aging On The Properties Of Glassy Polycarbonate, Kyle W. Strabala

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Physical aging and plastic flow are known to cause changes in the properties of glassy polycarbonate (PC). Although the individual effects of physical aging and plastic flow have been studied, the combined mechanical and thermal effects have yet to be evaluated for PC at large plastic strains. This work is the first characterization of the combined effects in PC of large plastic flow followed by thermal (physical) aging. To conduct this study, samples were prepared with different extents of plastic compressive strain, up to approximately 50% engineering strain, followed by thermal aging up to 135 °C, with various …

Multiscale Modeling Of Glass Fiber Reinforced Viscoelastic Polymers Subjected To Impact Loads, Victor Ferreira Teixeira

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

New applications for polymer composite materials are occurring at a rapid pace today. These include structural components in the energy, transportation, and biomedical fields.  Many if not all of these new applications will require that part performance is insured with some degree of sustainable damage.  With the growth in the use of composite structures comes the necessity of improved methodologies that can predict more accurately the life and serviceability conditions of composite parts. Damage mechanics in two-phase composite materials is a very complex problem that has challenged researchers for many years. However, most of the available models perform only a …

Me-Em Enewsbrief, June 2009, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Multiscale Modeling Of Impact On Heterogeneous Viscoelastic Solids With Evolving Microcracks, Flavio V. Souza

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Multiscale computational techniques play a major role in solving problems related to viscoelastic composite materials due to the complexities inherent to these materials. In the present work, a numerical procedure for multiscale modeling of impact on heterogeneous viscoelastic solids containing evolving microcracks is proposed in which the (global scale) homogenized viscoelastic incremental constitutive equations have the same form as the local scale viscoelastic incremental constitutive equations, but the homogenized tangent constitutive tensor and the homogenized incremental history dependent stress tensor depend on the amount of damage accumulated at the local scale. Furthermore, the developed technique allows the computation of the …

Identification Of Multiple Oscillation States Of Carbon Nanotube Tipped Cantilevers Interacting With Surfaces In Dynamic Atomic Force Microscopy, Mark Strus, Arvind Raman

Birck and NCN Publications

Carbon nanotubes (CNTs) have gained increased interest in dynamic atomic force microscopy (dAFM) as sharp, flexible, conducting, nonreactive tips for high-resolution imaging, oxidation lithography, and electrostatic force microscopy. By means of theory and experiments we lay out a map of several distinct tapping mode AFM oscillation states for CNT tipped AFM cantilevers: namely, noncontact attractive regime oscillation, intermittent contact with CNT slipping or pinning, or permanent contact with the CNT in point or line contact with the surface while the cantilever oscillates with large amplitude. Each state represents fundamentally different origins of CNT-surface interactions, CNT tip-substrate dissipation, and phase contrast …

Convergence, Adaptive Refinement, And Scaling In 1d Peridynamics, Florin Bobaru Ph.D., Mijia Yabg Ph.D., Leonardo F. Alves M.S., Stewart A. Silling Ph.D., Ebrahim Askari Ph.D., Jifeng Xu Ph.D.

Department of Engineering Mechanics: Faculty Publications

We introduce here adaptive refinement algorithms for the non-local method peridynamics, which was proposed (in J. Mech. Phys. Solids 2000; 48:175–209) as a reformulation of classical elasticity for discontinuities and long-range forces. We use scaling of the micromodulus and horizon and discuss the particular features of adaptivity in peridynamics for which multiscale modeling and grid refinement are closely connected. We discuss three types of numerical convergence for peridynamics and obtain uniform convergence to the classical solutions of static and dynamic elasticity problems in 1D in the limit of the horizon going to zero. Continuous micromoduli lead to optimal rates of …

Me-Em 2009 Annual Report, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering Annual Reports

Table of Contents

• Energy Systems
• Health Systems
• Faculty & Staff
• Students
• Alumni
• Resources
• Graduates
• Publications
• ME-EM Community

Me-Em 2008 Annual Report, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering Annual Reports

Table of Contents

• Engineering Education
• Students
• Alumni
• Resources
• Graduates
• Publications
• ME-EM Community

Me-Em 2007 Annual Report, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering Annual Reports

Table of Contents

• Research Expansion
• Research Groups
• Faculty & Staff
• Students
• Alumni
• Resources
• Graduates
• Publications

Influence Of Van Der Waals Forces On Increasing The Strength And Toughness In Dynamic Fracture Of Nanofibre Networks: A Peridynamic Approach, Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

The peridynamic method is used here to analyse the effect of van der Waals forces on the mechanical behaviour and strength and toughness properties of three-dimensional nanofibre networks under imposed stretch deformation. The peridynamic formulation allows for a natural inclusion of long-range forces (such as van der Waals forces) by considering all interactions as ‘long-range’. We use van der Waals interactions only between different fibres and do not need to model individual atoms. Fracture is introduced at the microstructural (peridynamic bond) level for the microelastic type bonds, while van der Waals bonds can reform at any time. We conduct statistical …

Statistical Interpretation Of Mohr-Coulomb Theory As Applied To Fracture In Brittle Materials Containing Cracks, Mudit J. Monsi

Mechanical & Aerospace Engineering Theses & Dissertations

Fracture in brittle materials containing pre-existing cracks was studied. The probability of of crack growth under both shear and tensile stresses was determined for an arbitrary distribution of crack sizes. Two different crack orientation distributions, random and uniform, as well as friction were also taken into account. The material's reliability was assumed to depend on the number of active cracks at a particular stress level, and this was expressed as an arbitrary 2-parameter Weibull distribution. Two new and efficient methods for calculating crack growth probabilities based on spherical triangles and spherical caps were developed. They utilized normalized stress coordinates and …

Socio-Economic Impacts Of Computer Viruses In Tanzania, M Victor

Tanzania Journal of Engineering and Technology (TJET)

This paper reports on a research project conducted with an objective of identifying and assessing various approaches used by different computer users (Management, System Administrators and end users) in Tanzania to combat computer viruses (CVs), and to assess users' awareness level on CVs. Specifically, the study aimed at assessing the awareness level on CVs to the Tanzanian business community; analyze the socio -economic impact caused by CVs in Tanzania and; assess existing methods, capacity and limitations on controlling CVs in Tanzania. Data was collected using both questionnaires and interview from financial institutions such as NBC and BOT, and telecommunications sector …